|Protein|Natural Host|Normal Function|Prion State|Prion Phenotype|Year Identified|
|---|---|---|---|---|---|
|Ure2p|Saccharomyces cerevisiae|Nitrogen catabolite repressor|[URE3]|Growth on poor nitrogen sources|1994|
|Sup35p|Saccharomyces cerevisiae|Translation termination factor|[PSI+]|Increased levels of nonsense suppression|1994|
|HET-S|Podospora anserina|Regulates heterokaryon incompatibility|[Het-s]|Heterokaryon formation between incompatible strains|1997|
|vacuolar protease B|Saccharomyces cerevisiae|death in stationary phase, failure in meiosis|[β]|failure to degrade cellular proteins under N starvation|2003|
|MAP kinases|Podospora anserina|increased pigment, slow growth|[C]||2006|
|Rnq1p|Saccharomyces cerevisiae|Protein template factor|[RNQ+],[PIN+]|Promotes aggregation of other prions|2008|
|Mca1*|Saccharomyces cerevisiae|Putative Yeast Caspase|[MCA+]|Unknown|2008|
|Swi1|Saccharomyces cerevisiae|Chromatin remodeling|[SWI+]|Poor growth on some carbon sources|2008|
|Cyc8|Saccharomyces cerevisiae|Transcriptional repressor|[OCT+]|Transcriptional derepression of multiple genes|2009|
|Mot3|Saccharomyces cerevisiae|Nuclear transcription factor|[MOT3+]|Transcriptional derepression of anaerobic genes|2009|
|Pma1+Std1|Saccharomyces cerevisiae|Pma1 = major plasma membrane proton pump, Std1=minor pump|[GAR+]|Resistant to glucose-associated repression|2009|
|Sfp1|Saccharomyces cerevisiae|Global transcriptional regulator|[ISP+]|Antisuppressor of certain sup35 mutations|2010|
|Mod5|Saccharomyces cerevisiae||[MOD+]||2012|

Question: how many prions have been characterized?
Answer: 13